With tiny parts, your cycle time will be 95% determined by the spindle RPM. Better motion control and faster toolchanges could shave that last 5%. Is a 5% shorter cycle time worth 5x to 10x the machine price?
Can I gently disagree here? And I say this, stating up front that I'm a beginner and almost certainly less experienced than yourself, I'm only making an observation.
I would agree if we were to imagine that we had already bought the best tools possible, optimised the program for the machine perfectly and were dominated by time in the cut. However, my limited experience suggests that variables such as machine accelerations, tool runout and to some extent tool quality (eg CTS vs non CTS) are able to make quite a significant difference on cut time?
Here's a post I put on my insta where I was running the same faceplate operation (0.5mm to 3mm tools) and the only difference was knocking the rapid knob on the Speedio from 5 to 4. Difference was 4:20mins to 5:10 mins cycle time. So not far off a minute slower or 25% slower, just by reducing the speeds of the rapids, ie slowing down *non cutting* time (you can see some pictures of the finished part in other posts - it's a faceplate for an electrical enclosure)
Now, I don't claim that someone else couldn't create a far better program! However, just an anecdote: On this program, much of the cutting time is taken on the tiny LED holes that are 1.5mm across and something like 3mm in length. However, the Brother has several features which allowed me to drop the machining time by about a factor of 3.
- Tool change time is so low (sub 2 seconds) that I can do a 1.5mm slot op, then a 1mm rough, then a 0.5mm finish. Using 3 tools is a massive time save (over say 2 tools, or even using only the 0.5mm alone).
- Acceleration is >1G. This means you can hit 10,000mm/min in <1mm of distance. So for example a similar part has a 2.1mm wide slot for a SIM card. The adaptives into the corner of that 2.1mm slot (0.08") have a 10,000mm/min non engagement move set on them and quite often it's hitting that (or close to) on repositioning moves!
- Same bonkers acceleration on the Z (actually it's faster, >2G accel on Z...). So repositioning moves pop up and down into the cut at 10m/min on my 0.5mm tool, could go faster still... This often halves my op time vs if instead I had forgotten to change the tool defaults
- Repositioning across the table, rapids are 50k/min. Sometimes Fusion360 does stupid moves where its adaptive will jump to both extremes of the job. I have in the past invested time getting rid of this, only to find it saves sub second time on the job... Not saying it's good to have an inefficient op, but the time cost for this is not so high (the programmer time is not free)
I would add high quality collets or tool holding + CTS as having a big effect on cut time. However, it's true that those could be applied to any (decent) machine. I find I can push tools much harder than I ever expected now (and that the manufacturer recommended...)
I don't think the Brother machine necessarily counts as a "super accurate" micro milling machine. To be fair I suspect other brands might do this job better and more accurately? I certainly find the dimensional accuracy in X and Y is accurate beyond my measuring equipment/ability to check it. However, work holding variations mean that I am probably worse than 0.02mm in Z on a regular basis. Not important for my work, but worth noting if that were part of the brief
However, what DOES impress me is watching the tool change for the 0.5mm tool when on full rapids... The old tool flies up, you get the Brother tool change whir! Then that 0.5mm comes down in a blink of an eye at 50,000m/min towards the solid fixture
. Fusion has it rapiding into empty space, to stop at z=0 !!!
There is nowhere further for it to go!! Then it turns right and starts machining out the corners of the pocket... Every time it changes tool I'm always amazed that the tool is still there...! It impresses me anyway!